Earning Per Share and Earnings Per Unit - Computation of Net Income per Share Basic and Net Income per Share Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 223,846	$ 144,196	$ 562,804	$ 498,297
Allocation to Noncontrolling Interests – Operating Partnership	(8,159)	(5,166)	(20,517)	(17,931)
Partially Owned Properties	(750)	(801)	(1,939)	(2,354)
Preferred distributions	(773)	(772)	(2,318)	(2,318)
Net income available to Common Shares	214,164	137,457	538,030	475,694
Numerator for net income per share – diluted	$ 222,323	$ 142,623	$ 558,547	$ 493,625
Weighted average Common Shares outstanding	368,028	366,996	367,920	366,809
Dilutive Op Units	12,884	12,910	12,871	12,907
Dilutive Securities Options	2,972	3,039	2,642	2,924
Weighted average Common Shares outstanding	383,884	382,945	383,433	382,640
Net income available to Common Shares	$ 0.58	$ 0.37	$ 1.46	$ 1.30
Net income available to Common Shares	$ 0.58	$ 0.37	$ 1.46	$ 1.29